Kinetic study of efficient visible-light-driven photocatalytic degradation of some organic pollutants over novel nanoparticle - graphene surfaces

Abstract

TiO2 is the most widely used photocatalyst in heterogeneous photocatalysis. However, its practical applications are diminished by fast electron-hole recombination, low adsorptivity and large band gap. This thesis is aiming to improve the photocatalytic performance of titania nanoparticles through design of three model systems which are TiO2/graphene, Bi4Ti3O12/TiO2 and Bi4Ti3O12/TiO2/ graphene nanocomposites by simple sol-gel and mechanical methods. The physicochemical properties of the nanocomposites were investigated using developed techniques as XRD, HRTEM, BET, PL, FTIR and DRS. The photocatalytic activity of the heterostructure photocatalysts was evaluated through degradation of methylene blue and p-aminophenol organic pollutant under UV and natural sunlight irradiation. In addition, kinetic study for the photocatalytic degradation reaction was carried out in order to investigate the effect of several factors such as catalyst dose, initial concentration and initial pH of the solution on the degradation reaction and get the optimum conditions. The results revealed that (1) graphene succeeded in reducing charge recombination, enhancing adsorptivity and UV photocatalytic reactivity in TiO2/graphene nanocomposites. (2) Bi4Ti3O12 /TiO2 Showed an enhanced sunlight photocatalytic reactivity due to lowering the band gap of TiO2. (3) The novel three- phases heterostructure Bi4Ti3O12/TiO2/ graphene photocatalyst was found to have a triple effect as it efficiently separated the charge carriers, enhanced adsorption capacity and reduced the gap energy of TiO2 nanoparticles.